Re: optimizing compiler against iaverage assembly programmer.

George C. Lindauer wrote:
>
> I was thinking about the assertion 'a good optimizing compiler will
> nearly always outcode a moderately proficient assembly programmer'.
>
> 1) What does the average assembly programmer do with the linkage
> between procedures? Does a good compiler still beat this? How does
> that affect the proposition?


A good one can optimize what registers are passed with what values,
and know what registers are not clobbered (and can hold values across
the call) i.e. interprocedural register allocation. So can a good
optimizing compiler.


>....
> Are good optimizing compilers really all they are cracked up to be?


I routinely see a 2x speed improvement for using the optimizer. More
for tuned routines (ala Spec benchmarks), sometimes much more.
Writing a good Matrix Multiply is hard, but if you write a simple one
darned if most compilers these days don't up and do something really
fancy with it. ;-)




> [Other important points: compilers make it a lot easier to use complex
> data structures,


I think this one falls under the catagory of using _any_ compiler,
optimizing or not.


> and compilers don't get bored halfway through and generate
> reliably pretty good code. -John]


Yup.


Cliff


--
Cliff Click, Ph.D. Compiler Researcher & Designer
RISC Software, Motorola PowerPC Compilers
cliffc@risc.sps.mot.com (512) 891-7240
--

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